It has long been standard practice to dispense fuels, such as gasoline, through measuring devices utilizing pistons which reciprocate back and forth in a cylindrical chamber with each complete stroke measuring a known unit volume of the liquid. It has been a problem in the past that these devices are truly accurate only for a quite limited portion of their total range of operating speeds. It is one of the objectives of this invention to materially increase the speed range throughout which the meter maintains its accuracy. Another problem with fuel metering devices of this type is that of maintaining accuracy of measurement over a reasonable operating life of the equipment. Wear has always been a serious problem. When the equipment is so made that it is extremely accurate, the equipment has the functional problem of being sensitive to dirt in the fuel and to variations in temperature, among other things. Therefore, all equipment, in effect, has been a compromise between accuracy, length of life and practical functionality in the field.
Another problem which has become increasingly difficult, as service stations have become larger and designed to service a greater number of vehicles simultaneously, has been that of how to maintain and improve accuracy and, at the same time, make the equipment more compact, simpler and more lightweight. It has also become very important to make the equipment capable of adaptation during assembly to the space requirements of the different pump chassis. Thus, it has become very desirable and important to design the unit such that it is capable of being quickly adapted to the requirements of the particular installation.